The maximum Byzantine victory over the Persians should be accomplished in the same way that the best Byzantine victories all are -- sneakily.
Thus ...
Emperor Maurice is a bit less hard on his soldiers, so Phocas never overthrows him. This butterflies away the Byzantine-Persian war of...
Hmm ... to follow up to this, some things are quite impossible. Sealion is probably one of them. However, and this is a pet peeve of mine, sometimes people are too quick to dismiss the low-probability result. This shows up particularly in discussions of WWII. Yes, the Axis was in a bad spot...
Some thoughts
I was reading this thread, while pondering my last trip through the archives (Confederate Victory! Nappy Wins! Germans don't make silly mistakes!), and some ideas came to mind. I hope I can supply some food for thought...
First, the preponderance of Western-oriented timelines...